Allyl Isothiocyanate Increases MRP1 Function and Expression in a Human Bronchial Epithelial Cell Line

Multidrug resistance-associated protein 1 (MRP1), a member of the ATP-binding cassette (ABC) superfamily of transporters, plays an important role in normal lung physiology by protecting cells against oxidative stress and toxic xenobiotics. The present study investigates the effects of allyl isothiocyanate (AITC) onMRP1mRNA and MRP1 protein expression and transporter activity in the immortalised human bronchial epithelial cell line 16HBE14o-.MRP1mRNA and MRP1 protein expression in 16HBE14o- cells that were treated with allyl isothiocyanate were analysed by real-time PCR assay and Western blotting. The transport of carboxyfluorescein, a known MRP1 substrate, was measured by functional flow cytometry to evaluate MRP1 activity. Treatment with AITC at concentrations of 5–40 μM increased MRP1 protein levels in a concentration-dependent manner. AITC treatments at concentrations of 1–40 μM caused concentration-dependent increases inMRP1mRNA levels that were up to seven times greater than the levels found in control cells. Finally, AITC treatment at concentrations of 5–40 μM significantly increased MRP1-dependent efflux in 16HBE14o- cells. These results suggest that AITC can increase the expression and activity of MRP1 in 16HBE14o- cells in a concentration-dependent manner. The upregulation of MRP1 activity and expression by AITC could produce therapeutic effects in the treatment of lung disease.

A New Azafluorenone from the Roots of Polyalthia cerasoides and its Biological Activity

Chromatographic separation of the ethyl acetate extract of roots of Polyalthia cerasoides has led to the isolation of the new compound, 6,8-dihydroxy-7-methoxy-1-methyl-azafluorenone. This compound exhibited potent cytotoxic activities with IC50 values in the range of 2.64-3.58 μg.mL−1 for A549, GLC4 and GLC4/Adr cells, but was not recognized by ABCC1/MRP1 protein. The compound also showed very strong inhibition of M. tuberculosis using a broth microdilution method, with an MIC value of 0.78 μg.mL−1, which was equal to that of ofloxacin, one of the four antibiotic drugs used as a positive control.

The Effect of Phenylhexyl Isothiocyanate on Drug Resistance of K562/A02 Cell Line

Objective: To investigate the effect of 6-phenylhexyl isothiocyanate (PHI) on drug resistance and sensitivity on K562/A02 cell line to ADM and elucidate the probable mechanisms. Methods: We measured growth inhibition of ADM on K562/A02 cell line by MTT assay. Apoptosis rate of K562/A02 cell line, the change of intracellular ADM and MRP1 protein level were detected by Flow Cytometry. Intracellular deoxidized GSH by spectrometric enzyme assay and MRP1 mRNA by RT-PCR semiquantitative assay were observed anteroposterior using PHI. Results: PHI can enhance the sensitivity of K562/A02 cell line to ADM, survival rate of K562/A02 cell line decreased with the increasing concentration of PHI and ADM. Apoptosis rate increased with treating by combination of two above drugs, and multiple of drug resistance had statistical significance (P<0.05) when the concentration of PHI was more than 20μmol/l. Intracellular GSH of K562/A02 cell line reduced 5% when 1μg/ml ADM was single used, and when more than 10μmol/l PHI was used it increased slightly at first then decreased. When more than 20μmol/l PHI and 1μg/ml ADM were used combination, intracellular GSH of K562/A02 cell line decreased progressively with increasing the concentration of PHI. Protein and gene level of MRP1 have no statistical significance (P>0.05) no matter after or before PHI was used on different concentration. Conlusion: The depletion effect of PHI on the intracellular GSH can not only partly enhance the reverse effect of ADM, but also enhance the sensitivity of K562/A02 cell line to ADM. Such depletion may diminish side effect and treatment dosage of ADM. It provides a new view to the therapy of leukaemia.

Multidrug resistance-associated protein--reduction of expression in human leukaemia cells by antisense phosphorothioate olignucleotides.

Multidrug resistance-associated protein (MRP1) causes cellular drug resistance in several cancer cell lines. In this paper we show that antisense oligonucleotides decrease MRP1 expression in human leukaemia cells. We investigated biological activity of a series of 12 linear phosphorothioate oligonucleotides, complementary to several regions of MRP1 mRNA. The oligonucleotides were administered to leukaemia HL60/ADR cells overexpressing MRP1 protein. Then, the level of MRP1 mRNA was determined by means of semiquantitative RT-PCR and the protein level by reaction with specific monoclonal antibodies. Some of the investigated antisense oligonucleotides decrease the expression level of the MRP1 protein by 46% and its mRNA level by 76%.

Multidrug Resistance Protein 1 Protects the Oropharyngeal Mucosal Layer and the Testicular Tubules against Drug-induced Damage

The multidrug resistance protein 1 (MRP1) gene encodes a transporter protein that helps to protect cells against xenobiotics. Elevated levels of MRP1 in tumor cells can result in active extrusion of a wide range of (anticancer) drugs with different cellular targets, a phenomenon called multidrug resistance (MDR). To explore the protective function of the mouse mrp1 protein during drug treatment, we investigated the toxicity caused by the anticancer drug etoposide-phosphate (ETOPOPHOS) in mice lacking the mrp1 gene (mrp1−/− mice). We show here that the lack of mrp1 protein results in increased etoposide-induced damage to the mucosa of the oropharyngeal cavity and to the seminiferous tubules of the testis. The high concentrations of mrp1 that we find in the basal layers of the oropharyngeal mucosa and in the basal membrane of the Sertoli cells in the testis apparently protect wild-type mice against this tissue damage. We also find drug-induced polyuria in mrp1−/− mice, which correlates with the presence of mrp1 protein in the urinary collecting tubules, the major site of kidney water reabsorption. Our results indicate that specific inhibitors of MRP1 used to reverse MDR, in combination with carcinostatic drugs transported by MRP1, might lead to drug-induced mucositis, (temporary) infertility, and diabetes insipidus.